1. Field of The Invention
This invention generally relates to a laser treatment device used for a medical treatment to be performed by irradiating laser light, which is transmitted through an optical fiber from a laser light source, on an object and more particularly to a laser treatment device suitable for a medical treatment of a hard tissue (e.g., a tooth) to be irradiated.
2. Description of the Related Art
Generally, in each conventional laser treatment device, a probe for guiding laser light, which is output from an optical fiber for transmitting laser light, to an object to be irradiated is provided at an output end of the optical fiber. Further, there are publicly-known two types of probe. One is a non-contact type of probe as disclosed in, for example, Japanese Unexamined Patent Publication (Kokai Tokkyo Koho) Official Gazette No. 61-20544, which does not contact an object to be irradiated. The other is a contact type of probe as disclosed in, for instance, Japanese Unexamined Patent Publication (kokai Tokkyo Koho) Official Gazette No. 63-318934, which contacts an object to be irradiated.
A probe of the non-contact type is operative to irradiate laser light output (namely, emitted) from the output end of the optical fiber on the object by converging the output laser light on a spot having a predetermined spot size thereon. Further, a probe of the contact type is formed as an individual device other than the optical fiber by using, for example, a sapphire rod and abrading (namely, tapering) the sapphire rod in such a manner that the diameter of the transverse section of the probe becomes smaller gradually toward one end thereof. Furthermore, the laser light output from the output end of the optical fiber impinges on the probe of this type and thereafter undergoes an internal reflection on an abraded surface. As the result, the reflected laser light is converged on an end portion of the probe of this type and is then irradiated on the object by bringing the end portion of this probe into direct contact with the object.
Incidentally, in case of another laser treatment device manufactured by, for example, Laserscope Inc. of U.S.A., an output portion of an optical fiber for transmitting laser light is used as a probe of the contact or non-contact type.
Additionally, in recent years, an Er:YAG laser (namely, E.sub.r.sup.S+ laser) has been developed as a laser light source, by which a hard tissue, as well as a soft tissue, can be processed. Consequently, a laser treatment device can be used for a medical treatment of dentin (or dentinum) or enamel by employing such a laser.
The aforesaid conventional laser treatment devices, however, have encountered the following problems.
First, the diameter of the converging lens employed in the probe of the non-contact type is at least 1 millimeter (mm) .PHI. or so. Namely, it is difficult to make a probe of this type, the converging lens of which is less than 1 mm .PHI. in diameter. Thus, in case of a medical treatment of the inside of a narrow diseased region (for example, a crooked root canal, which is not more than 500 microns (.mu.m) .PHI. in diameter, or a periodontal concavity (i.e., a periodontal pocket)), a deep part of the diseased region cannot be sufficiently irradiated with laser light.
Moreover, although an end of an ordinary probe of the contact type is 0.3 mm .PHI. in outer diameter or so, a base of the tapered portion thereof is thick and 2 mm .PHI. or so in outer diameter. Therefore, similarly as in case of the probe of the non-contact type, a deep part of an affected region cannot be sufficiently irradiated with laser light.
In contrast, in case where the output end of the optical fiber is used as a probe, even a deep part of an affected or diseased region can be sufficiently processed. However, in case of such a type of probe, the output end of the optical fiber may melt due to heat produced at the time of irradiation. Further, matters scattered at the time of irradiation sometimes adhere to the output end of the optical fiber. Moreover, the output end of the optical fiber, to which the scattered matters adhere, may melt as a result of being heated by laser light. Such a melting of the output end of the optical fiber and an adhesion of the scattered matters thereto result in that the intensity of laser light output therefrom becomes uneven and the performance of the probe becomes deteriorated and that additionally, after such an output end of the optical fiber is used as a probe, it becomes impossible to perform a medical treatment of soft tissues by fitting an ordinary probe of the contact type made of sapphire or the like, which has been separated from the optical fiber, to such an output end thereof.
Further, especially in case of performing a medical treatment of hard tissues such as dentin by using an Er:YAG laser, it is preferable for effectively preventing vaporized matters, which are generated at the time of performing the medical treatment, from adhering to dentin or the like to spurt washing water from the vicinity of a probe simultaneously with outputting laser light. However, there has been raised a problem that an optical fiber including a fluoride (hereunder sometimes referred to as a fluoride fiber), which can efficiently transmit laser light output from an Er:YAG laser, is liable to influence of water or moisture.